Build infinite scroll

• Loads the first page from a mocked paged API (with a delay), and loads the next page when a sentinel element near the bottom becomes visible, using IntersectionObserver
• Shows a loading indicator while fetching and does not start a second request while one is in flight
• On failure, shows an error row with a Retry button and stops auto-loading until retry is clicked
• Pages are deduplicated by item id, so overlapping pages or a double trigger never render an item twice
• When the API reports no more pages, shows an "End of list" message and disconnects the observer
• Handles an empty first page with an empty state
• Cleans up the observer on unmount and when the sentinel changes

Only after every requirement works.

• Use rootMargin to prefetch before the sentinel is on screen
• Virtualise the rendered rows for very long lists
• Preserve scroll position and loaded pages when navigating away and back